This invention relates generally to developer stations for electrographic copiers, and more particularly to a developer station in an electrographic copier utilizing a plurality of moving discrete dielectric sheets for developing latent image charge patterns carried by such sheets.
In U.S. Pat. No. 4,436,405 issued Mar. 13, 1984 in the name of Kindt, an electrographic copier is described which utilizes a plurality of discrete photoconductive sheets. The sheets are transported seriatim about a continuous path into operative relation with electrographic process stations to make information reproductions. In the reproduction process carried out at such process stations of the copier, a sheet is uniformly charged and then exposed by an image of information to be reproduced (e.g., a document) to form a latent image charge pattern on such sheet corresponding image-wise to such information. The charge pattern is developed with pigmented thermoplastic electroscopic marking particles electrostatically attracted to the charge pattern to form a transferable image. The transferable image is then transferred from the sheet to a receiver member to form the information reproduction, and the sheet is cleaned for reuse.
Development of the charge patterns on the discrete sheets is accomplished by a magnetic brush developer apparatus such as shown in U.S. Pat. No. 3,703,395 issued Nov. 21, 1972 in the name of Drexler et al, for example. In typical magnetic brush developer apparatus, developer material including pigmented electroscopic marking particles adhering to magnetizable particles (or single component material where the pigmented particles are magnetizable) are brought into a magnetic field intercepting the path of a charge pattern carrying member. The magnetizable particles align in the field to form brush-like bristles of pigmented particles which contact such member. The pigmented particles are electrostatically attracted to the charge pattern and adhere to such pattern for development. However, when the charge pattern carrying member is a plurality of discrete sheets, there is a propensity for such sheets to plow through the bristles. This can lead to deposition of developer material on the back side of the sheets. Therefore, cleaning of the sheets is made more complex (i.e. cleaning of the back sides must also be effected). Moreover, contamination within copier environment by airborne developer material, or non-transferred developer material carried out of the developer station by the sheets, is potentially increased.